In communications networks, such as long term evolution (LTE) networks, the PCRF is the node that executes user policies that control aspects of a user's network services, such as authentication, authorization, bandwidth, other quality of service features, etc. A PCRF may obtain the policies for subscribers from another node referred to as a subscription profile repository (SPR), which may be co-located with a home subscriber server (HSS). The PCRF may communicate with a policy and charging enforcement function (PCEF), which enforces policies for subscriber terminals. When a user first communicates with a network, the user is assigned to a PCRF. Once a PCRF has been assigned, subsequent session related traffic for the user must be sent to the same PCRF because the PCRF stores policy state for the user. For example, the PCRF may store the volume of data accessed by the user while the user is attached to the network. The user's policy maintained by the PCRF may specify that the user's network access bandwidth is to be adjusted once the volume of accessed data reaches a threshold level. In order to manage such a policy, all traffic intended for the user during a particular network attachment must traverse the same PCRF.
More generally, when a node seeks to establish a session with the user, the node may contact the PCRF to request a particular level or quality of service for the session. The PCRF may execute the user's policy and respond to the request, indicating the quality of service that will be provided for the session. The PCRF may instruct the PCEF to enforce the policy as communicated to the requesting node.
Another function performed by the PCRF is charging. The PCRF may implement charging on a per packet flow basis. Packets matching filters of a particular policy rule are referred to as a service data flow (SDF). By identifying all packets associated with the same flow, the PCRF may charge for the flow in accordance with policy rules defined for the subscriber.
A DRA is responsible for routing or relaying Diameter signaling messages between Diameter nodes. In networks with very few Diameter nodes (such as PCRFs), there may be little need for a DRA. However, as the number of subscribers served by a network increases, it is necessary to scale the policy control functionality of the network and thus to add PCRFs and other Diameter nodes to the network. With plural PCRFs, it may be necessary to add plural DRAs to the network. While DRAs route Diameter signaling messages based on Diameter parameters, the base Diameter protocol specified in IETF RFC 3588 does not specify a methodology for selecting a PCRF in a network with plural PCRFs. As set forth above, there is a need to assign a PCRF to a user when the user first connects or attaches to the network and to ensure that subsequent session related traffic for the user is routed to the same PCRF. When there are plural DRAs and/or PCRFs in a network, optimally assigning subscribers to a PCRF and ensuring the proper routing of signaling after assignment has been made become important.
Accordingly, there exists a need for methods, systems, and computer readable media for PCRF node selection.